| 摘要 |
In a bumper system suitable for stopping tree trunks fed lengthwise in positions for cutting successive equal lengths from the trunk, a bumper system is provided which absorbs tree trunk momentum by dissipation of energy and stops the tree trunk in position for sawing. Subsequent binding of the cut lengths between the face of the bumper and the saw is prevented by further receding movement of the bumper. Using a three-port cylinder, the impact moves the piston inward to expel hydraulic fluid through the intermediate port in series with a relief valve which provides resistive back pressure. At the predetermined correct measuring position, the piston closes this intermediate port, temporarily stopping the bumper and the tree trunk. During cutting, the more remote port is opened and oil is supplied to the near port to retract the bumper out of the way.
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